The following is provided as background only; nothing in this section is intended to be, nor should any of it be construed as, prior art to the present invention.
Rope ladders have many uses. For example, they serve as emergency escape means from buildings and other structures. They also are used as boarding and disembarking means for ships at sea, in particular by local pilots who board ships coming into harbor to assume responsibility for docking them. To reduce any contribution of the rope ladders themselves to the substantial risks involved when using them to embark or disembark a ship, the Coast Guard has mandated rigid specifications to which marine-use rope ladders must adhere. To this end, a number of patents have been issued relating to rope ladders, in particular to the steps of the ladders and to the means by which the steps are secured to the ropes.
One of the earliest patents relating to rope ladders as modernly conceived is U.S. Pat. No. 4,177,878, to Salvarezza, filed 14 Aug. 1978, issued 11 Dec. 1979. Originally, the steps used for rope ladders were made of wood and were susceptible to warping, breakage and general structural non-uniformity. The advent of superior strength polymers led to the development and use of steps made of hard, tough, durable polymeric materials. Thus, U.S. Pat. No. 4,241,809 to Salvarezza, filed 13 Aug. 1979 and issued Dec. 30, 1980, also to Salvarezza, is directed to a rope ladder with a molded hard elastomer step and a method for assembling ladders using such steps. Another patent, U.S. Pat. No. 4,554,996, likewise to Salvarezza, filed 12 Apr. 1985, issued 26 Nov. 1985, is directed to additional features of molded hard elastomer rope ladder steps as well as to replacement steps and collars. U.S. Pat. No. 4,655,321, again to Salvarezza, filed 29 Aug. 1986 and Issued Apr. 7, 1987, adds to the art an improved method for assembling rope ladders comprising molded hard elastomer steps and U.S. Pat. No. 4,683,981, to Salvarezza, is directed to molded hard elastomer steps having additional features, to replacement and spreader steps and to novel methods of molding the steps. Each of the preceding patents is incorporated by reference, including all drawings, as if fully set forth herein.
While the means for securing the steps to ropes in the above patents surpass all Coast Guard specifications with regard to load-bearing without rope slippage, even greater non-slippage capability, and therefore an even greater margin of safety, is always desirable. The present invention provides a means for securing ropes to the steps of rope ladders that renders the likelihood of slippage of the steps along the rope vanishingly small under virtually any load.